As a lamp of this type, one has been known in which a plurality of optical system units used in different purposes are accommodated in a lamp chamber. For example, Japanese Patent Laid-Open Publication No. 2010-267468 discloses a lamp for a vehicle in which a first optical system unit constituting a head light configured to illuminate a predetermined area in front of the vehicle and a second optical system unit constituting a daytime running light used to notify the presence of the vehicle to other vehicles or pedestrians in front of vehicle are accommodated in a lamp chamber.